MARMAM Community,
On behalf of my co-authors I am pleased to announce the publication of a new paper on the behavioral responses of common dolphins to simulated and actual military active mid-frequency sonar signals. The paper reference, open access link, and abstract are included below.
Southall B.L., Durban, J.W., Calambokidis, J., Casey, C., Fahlbusch, J.A., Fearnbach, H., Flynn, K., Fregosi, S., Friedlaender,
A.S., Leander, S.G.M., and Visser, F. (2024). Behavioural responses of common dolphins to naval sonar. R. Soc. Open Sci.11:
240650.
Open Access and Other Relevant Links:
Abstract:
Despite strong interest in how noise affects marine mammals, little is known for the most abundant and commonly exposed taxa. Social delphinids occur in groups of hundreds of individuals that travel quickly, change
behaviour ephemerally, and are not amenable to conventional tagging methods, posing challenges in quantifying noise impacts. We integrated drone-based photogrammetry, strategically- placed acoustic recorders, and broad-scale visual observations to provide
complimentary measurements of different aspects of behaviour for short- and long-beaked common dolphins. We measured behavioural responses during controlled exposure experiments (CEEs) of military mid-frequency (3-–4 kHz) active sonar (MFAS) using simulated
and actual Navy sonar sources. We used latent-state Bayesian models to evaluate response probability and persistence in exposure and post-exposure phases. Changes in sub-group movement and aggregation parameters were commonly detected during different phases
of MFAS CEEs but not control CEEs. Responses were more evident in short-beaked common dolphins (n =14 CEEs), and a direct relationship between response probability and received level was observed. Long-beaked common dolphins (n = 20) showed less consistent
responses, although contextual differences may have limited which some movement responses could be detected. These are the first experimental behavioural response data for these abundant dolphins to directly inform impact assessments for military sonars.
Thanks for your interest and to all the study participants, funders and logistical support provided and acknowledged in the paper.
Brandon Southall on behalf of my co-authors
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